Punching bag



FIG. 1 is a perspective view of a punching bag showing my new design;

FIG. 2 is a top plan view of my newly designed punching bag;

FIG. 3 is a bottom plan view of my newly designed punching bag; and,

FIG. 4 is a front elevation view of my newly designed punching bag, the rear, left and right side elevation views being identical.

The broken line showing of the straps and strap rings in FIGS. 1, 2 and 4 is for illustrative purposes only and forms no part of the claimed design. 

I claim the ornamental design for a punching bag, as shown and described. 